Sound-attenuating system and apparatus for gas streams



I). 25-, 1962' F. E. DEREMER 3,070,187

- SOUND-ATTENUATING SYSTEM AND APPARATUS FOR GAS STREAMS Filed May. 18, 1959 2 Sheets-Sheet 1 J'Nvzw TUE: .TZL UYD E. .ZZEHEMER.

ATTYZ nited States Patent 0 3,il7il,187 SOUND-ATTENUA'l'rtNG SYSTEM AND APPA- RATUS FOR GAS STREAMS Floyd E. Deremer, Livonia, Mich., assignor to Oldberg Manufacturing Company, Grand Haven, Mich., a corporation of Michigan Filed May 18, 1959, Ser. No. 813,771 6 Claims. (Cl. 18155) This invention relates to sound-attenuating system and apparatus especially for use with dual exhaust gas streams from an internal combustion engine of the character empioyed in automotive vehicles, the system and apparatus functioning to attenuate sound waves entrained in the gas streams and to further equalization of irregular pressure impulses in the exhaust gas streams.

Eight cylinder engines of the internal combustion type embodying two parallel banks of four cylinders in each bank have come into extensive use for powering automotive vehicles, each bank of cylinders being equipped with an individual exhaust manifold which heretofore have been joined for conveying exhaust gas streams from both banks through a single muffler or sound-attenuating means. In other types of installations, dual exhaust gas duct arrangements are provided and each gas stream is conveyed independently of the other through one or more sound-attenuating mufflers in order to attenuate sound waves entrained in the exhaust gas streams.

"the trend of automotive construction is toward a lowering of the chassis frame and such design poses difiiculties in the positioning of sound-attenuating means or mufllers beneath the body due to the necessary presence of transversely extending frame struts or bracing members of the vehicle frame. Thus in exhaust systems of vehicles where high sound-attenuating efficiency is desired, two or more mufflers have been placed in series relation lengthwise of the vehicle for each exhaust gas stream. In this type of installation, the presence of frame cross members prevents the use of a single muffler or sound-attenuating means of a length sufficient to obtain proper sound-attenuation over a desired sound wave range.

In multi-cylinder engine constructions comprising two banks of cylinders wherein the pistons are connected to a single crankshaft, the firing order of ignition in the cylinders in each bank do not occur at regular intervals. In an eight cylinder engine having two banks of cylinders, successive firing of two cylinders occurs in each bank, the remaining cylinders firing alternately. During a complete cycle of firing of the eight cylinders, two successive exhaust impulses occur in the exhaust manifold for each of the banks of cylinders. These irregular pressure impulses in each exhaust manifold establish nonrhythrnic pulsations in the gas stream which are audibly exemplified by a distinct throbbing in each exhaust duct arrangement.

The present invention embraces a system and apparatus involving the positioning of sound-attenuating instrumentalities amidship and extending transversely of the vehicle and connected together by a pressure balancing or equalizing passage or tube whereby improved sound-attenuation is attained, particularly improved attenuation of the'sound waves set up by irregular exhaust or pressure impulses in dual exhaust gas streams.

An object of the invention is the provision of a system or method of flowing exhaust gas streams from two manifolds into sound-attenuating chambers disposed transversely of a vehicle and connected by a pressure equalizing or gas exchan e tube or passage in a manner whereb pressure impulses occurring at irre ular intervals are dissipated in the interconnected chambers whereby the Patented Dec. 25, 19-32 sound Waves of the irregular impulses are effectively attenuated or their audible effect minimized or rendered unobjectionable.

Another ob ect of the invention resides in the provision of a combination of sound-attenuating units or mufflers disposed amidship and extending transversely of a vehicle and interconnected by a balancing tube whereby effective sound-attenuation is attained and wherein the installation does not interfere with the frame members of the vehicle so as to provide for maximum roadway clearance.

A further object of the invention resides in the provision of dual sound-attenuating chambers or units arranged in series relation disposed transversely of a vehicle and interconnected by a passage whereby pressure impulses in the gases from engine exhaust manifolds are blended or balanced whereby objectionable audible throbbing in the exhaust gas streams is substantially eliminated. Another object is the provision of an apparatus or system involving multiple transversely extending and axially or longitudinally aligned rnufiler or sound-attenuating units connected at their adjacent end regions by tubular means whereby pressures of irregular impulses in the streams are substantially neutralized or equalized and the sound waves of the irregular impulses substantially attenuated.

Another object of the invention is the provision of multiple sound-attenuating units each embodying soundattenuating and resonator chambers adapted to receive multiple streams of exhaust gases from an internal combustion engine, the units being interconnected by a balancing tube providing for pressure balancing and blending of the gases of the streams and improved soundattenuation.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economics of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of-the invention, which may be preferred, in which:

FIGURE 1 is a schematic plan view of a vehicle embodying an exhaust system of the invention utilized with a multi-cylinder engine having dual banks of cylinders in parallel relation with sound-attenuating units arranged transv elv and amidship of the vehicle;

FIGURE 2 is a s"hematic e'evational view of the arran er ent portrayed in FIGURE 1;

FIGURE 3 is an enlarged longitudinal sectional view through cne form of sound-attenuating and gas blending unit of the multiple unit system of the invention;

FIGURE 4 is a transve"se secional view through the attenuaing unit illustrated in FIGURE 3, the view being taken sub tantially on the line 44 f FIGURE 3;

FIGURE 5 is a schematic longitudinal sectional view drawn to a reduced scale illustrating the interior arrangements in the multiple units or mufflers illustrated in FI URES 1 through 4;

FIGURE 6 is a schematic longitudinal sectional view drrwn to a reduced scale ilustrating a moified form of attenuati g unit and interconne tion between the units;

FIGURE 7 is a schematic sectional view drawn to a reduced scale i'lustrating the system embodying another form of sound-attenuating and impulse-equalizing interconn ted units; V

FIGURE 8 is a schematic longitudinal sec ional view drawn to a reduced scale illustrating dual sound-attenuating units with a combined connecting passage and gas outlet means between the units, and

FIGURE 9 is a schematic sectional View drawn to a reduced scale illustrating a modified form of exhaust inlet and outlet passage means for each of the sound-attenuating units of a system.

While the forms of apparatus of the system of the inveniicn discjosed herein have particular utility with dual exhaust gas streams of an internal combustion engine utilized as a power unit for an automotive vehicle, it is to be understood that the system and apparatus may be utilized wherever it is desired to attenuate sound waves entrained in the streams and equalize or neutralize irregular pressure impulses.

The illustrations of system and apparatus of the inventi:n for blending exhaust gas streams are shown in connection with an eight cylinder engine having two banks or blocks of four cylinders each, but it is to be understood that the system and apparatus may be utilized in connection with exhaust gas streams of engines having a different number of cylinders. With particular refern e to FIGURE 1, the outline of a top plan of a vehicle body is illustrated at 16, the body being supported upon a suitable frame or chassis structure (not shown), the vehicle being equipped with pairs of front and rear road wheels designated respectively 12 and 14.

Cradled in the forward region of the chassis frame and supported thereby is an internal combustion engine 18 of the eight cylinder type fashioned with two parallel banks or blocks of cylinders designated respectively 20 and 22, each bank being inclusive of four cylinders. The engine is connected through suitable power transmission mechanism contained in a housing 24 and a drive shaft construction 26 to the rear wheels 14 of the vehicle for driving the same in a conventional manner.

The bank of cylinders 20 is equipped with an exhaust manifold 28 having four branches in communication with the exhaust ports of the four cylinders in the engine block 20 through which exhaust gases from the cylinders are delivered into the manifold 28. The bank of cylinders 22 is equipped with a similar manifold 30. In eight cylinder engines comprising dual blocks of four cylinders each, several firing orders may be utilized, but in all firing orders two cylinders in each block are fired consecutively while the remaining cylinders in both blocks are fired alternately. One typical firing order of cylinders of an eight cylinder engine, with reference to the cylinder numbering shown in FIGURE 1 is 1, 5, 4, 8, 6, 3, 7 and 2.

Thus the successive firing of two cylinders in a block during engine operation produces or sets up successive pressure impulses in the gas streams in each of the manifolds 28 and 30. The successive pressure impulses in one manifold occur at a different period of time than the successive dual impulses in the other manifold. Hence the pressure impulses in both exhaust gas streams delivered fro-m the manifolds 28 and 30 are irregular and, when the gas streams are directed respectively through individual sound-attenuating means or mufflers, objectionable audible throbbing or pulsing sound are preseit.

In the present invention, the dual gas streams from the manifolds are fed into interconnected sound-attenuating and gas blending units wherein the irregular audible pressure waves are reduced or substantially attenuated and the pressure impulses substantially equalized through the medium of the interconnection between the sw-undattenuating units. In the arrangement or system of the present invention, the interconnected sound-attenuating mufflers or units are arranged in alignment and extend transversely of the vehicle.

The transversely disposed units are shaped and the interconnection therebetween disposed so that the units may be mounted amidships of the vehicle adjacent the rear of the housing containing the ptwer transmission mechanism, the individual units being mounted at opposite sides of the power transmission housing so as to provide maximum clearance above the roadway with the I positioning of the dual sound-attenuating and pressure equalizing units, FIGURES 3 and 4 illustrating a detailed form of one of the units and FIGURE 5 a semidiagrammatic sectional view of the dual unit installation of FIGURES 1 and 2. The arrangement shown in FIGURES 1, 2 and 5 includes substantially identical units 34 and 36, which are of the same construction, one of the units 34 being illustrated in detail in FIG- URES 3 and 4.

The exhaust manifold 28 is connected by means of an exhaust-conveying tube or elbow 38 into the inlet 40 of the unit 34 while the exhaust gas stream from the manifold 30 is conveyed by means of a tube or elbow 42 with the inlet 44 of the unit 36. The units 34 and 36 are connected together by means of a pressure equalizing or balancing tube 46 which, as shown in FIGURE 2, is disposed adjacent and beneath the drive shaft arrangement 26 at the rear of the power transmission housing 24 of the vehicle.

The sound-attenuating mufliers or units 34 and 36, as illustrated, are of identical construction and one of the units 34 is illustrated in detail in FIGURES 3 and 4. A description of one unit will suffice for both. As shown in FIGURES 2 and 4, each sound-attenuating unit is preferably of oval ellipsoidal in cross-section as this configuration enables maximum clearance between the roadway and the sound-attenuating unit or mufiler. Each of the units 34 and 36 is inclusive of a sheet metal shell construction 50 of generally oval or ellipsoidal shape as shown in FIGURE 4.

In the embodiment illustrated the shell is double walled, comprising an outer layer or shell 52 and an inner layer or shell 54, the outer layer being formed with spaced longitudinally extending ridges 56 which engage the inner layer 54 so as to space the layers apart providing longitudinally extending isolated regions or zones providing air chambers adapted to cushion vibrations and reduce shell noise. The inner and outer metal layers are joined by a seam 60 formed by overlapping regions of the layers bent upon themselves as shown in FIGURE 4.

Each of the attenuating units 34 and 36 is provided with end closures or heads 62 and 64, the peripheral regions of the end heads 62 and 64 being flanged as at 66 embracing the juxtaposed ends of the outer and inner layers 52 and 54 whereby the end heads are securely fastened to the shell construction providing sealed joints. The space between the inner and outer shell members 52 and 54 may accommodate a layer of asbestos or other heat resistant material having sound damping characteristics, the layer serving as heat insulation.

If desired, the shell construction 59' may be a single sheet of metal formed to tubular shape or a sheet of metal wrapped upon itself to form a multiple layer shell. In the shell construction shown in FEGURE 3, the ends of both layers 52 and 54 are brought into contiguous relation to receive the flanged regions of the end heads 62 and 64. Each of the end heads is formed with a ledge 63 which snugly fits within the end region of the inner shell and the flange 66 spun into the position shown in FIGURE 3.

Each of the units 34 and 36 is inclusive of gas passage means disposed Within the shell, he walls of the gas passage means being formed with small openings providing acoustic couplings for sound-attenuating purposes and for facilitating transverse or cross flow of gases within the shell construction. As particularly shown in Fit URE 3, the end closure 62 is provided with an opening accommodating the gas inlet coupling or tube 4% and a second coupling or tube 76 providing a gas outlet.

The end head 64 of each of the units 34 and 36 is provided with a central opening accommodating a tubular coupling 72, the couplings being connected by means of a balancing tube or tubular means 46 as shown in FIGURE 5. In the embodiment illustrated in FIGURES 1 and 2, the inlet coupling 40 of each unit is connected with an adjacent exhaust tube or elbow 3:8 and 42. As shown in FIGURE 3, each of the sound-attenuating and gas blending units includes gas passage tubes id and 76, the gas passage tube or means 74 being in communication with the coupling member 4-0 and receives exhaust gases from the adjacent manifold. The second gas passage tube or means 76 is in communication with the couplings 7 t) and 72.

There is provided interiorly of each of the units 34 and 36, one or more partitions or transversely extending walls which divide the interior into two or more compartments or chambers. As shown in FIGURE 3, there are three transversely disposed, longitudinally spaced walls or baflies 78, 79' and 80 providing sound-attenuating and gas transfer chambers 82, 83 and 34. The baffle 80 and the end head 64 provide a low frequency resonator chamber 85. Each of the transversely extending walls 78, 79 and 80 is of oval shape and is provided with a peripheral flange 86 of oval shape engaging the interior surface of the inner shell 54.

Surrounding the tube or gas passage means '76 is a second tube or tubular member 88 of larger diameter which is substantially concentric with the tube 76 and is held in this position by annular members 9-0, the members having flanged portions which respectively engage the outer surface of the tube 76 and the inner surface of the end regions of the tube 88. The walls or baflles 78, 79' and 80 are provided with openings to accommodate the tubes 74 and 88. The walls of the gas passage tubes 7 4 and 76 are provided with a large number of comparatively small openings 94 and 6, and the tube 38 provided with a substantial number of comparatively small openings 98.

The openings in the tubes 74, 76 and $8 form acoustic couplings with the adjacent regions within the shell for attenuating sound waves and for facilitating transverse or cross flow of exhaust gases from the inlet tube 74 through the adjacent chambers 82, 83 and do and through the openings 96 and 98 into the tube 76, the latter conveying the gases either through the balancing tube 46 to the other attenuating unit or through the outlet cou pling 7d and exhaust pipe 1% to the rear of the vehicle. this arrangement being schematically illustrated in FIG- URE 1.

Very little transfer of exhaust gases occurs in the connecting or balancing tube 46, this tube serving pri marily as a pressure balancing means whereby uneven pressure impulses in the exhaust gas streams are effectively equalized or neutralized. The annular space Hi2 provided between the tubes '76 and $8 is partitioned by annular members 1%, the compartments forming attenuating chambers for sound waves in the high frequency range.

The operation and functioning of the system and apparatus illustrated in FIGURES 1 through 5 are as follows: The exhaust gas streams in the exhaust manifolds 28 and 30 are delivered into the inlet couplings 4t and 4d at the outer ends of the units 34 and 36 whereby the exhaust gases from the respective manifolds are discharged or delivered into the tubes or gas passage means '74, the gases flowing transversely through the openings 94. One end of the tube 74 opens into the resonator or chamber 85 which serves to attenuate low frequency sound waves.

The compartments or spaces 102 between the tubes '76 and 88 form or provide high frequency sound wave attenuating means. The gases from the tube 74 flow transversely through openings 94 in the tube 74, openings 98 in the tubular member 83 and openings 96 in the tube 75, the exhaust gases being then discharged through the outlet coupling 7b of unit 34- and outlet coupling '70 of unit 36 into the exhaust pipes 1% for discharge rearwardly of the vehicle.

When successive pressure impulses occur in one of the manifolds by reason of the particular firing order of the cylinders, the pressure balancing tube 46 serves to assist in the equalization, neutralization or balancing of differential pressures in the intercoupled units 34 and 36 to smooth out the gas flow and promote improved attenuation of sound waves set up by the irregularity of pressure impulses in both sound-attenuating units 3% and 36.

It is found that by delivering exhaust gases into the outermost ends of transversely aligned sound-attenuating units, coupled by balancing tube 4-6, that sound waves in the objectionable audible wave range are satisfactorily attenuated without necessitating the use of additional sound-attenuating means. It is to be understood however that if desired, additional sound-attenuating means may be incorporated with the exhaust pipes N10.

While the arrangement as shown in FKGURES 1 through 5 illustrates the coupling members 4t? as the exhaust gas inlet, it is to be understood that the couplings may be connected with the exhaust manifolds 28 and 3t and utilized as the gas inlets into the units 34 and 3d. T he couplings 4G, in such an arrangement would be utilized as gas discharge outlets and same would be connected with the exhaust pipes 1th for conveying exhaust gases to the rear of the vehicle.

With the above described arrangement of muiliers or sound-attenuating units disposed transversely of and amidship of the vehicle at the rear of the transmission housing 2 an exhaust gas system is provided which does not interfere with the vehicle frame struts or members providing improved sound-attenuation and gas pressure or impulse balancing means which improves the flow of exhaust gases through the units and minimizes the audible throbbing resulting from irregular pressure impulses in the exhaust gas streams.

FEGURE 6 is illustrative of a modified sound-attenuating and pressure impulse balancing system. In this arrangement the sound-attenuating units the and M7 are of identical construction, each unit comprising a dual wall shell 116 provided with end heads 112 and lid which are joined to the shell in the manner shown described in connection with the form of unit illustrated in FIGURE 3. In the arrangement shown in FiGURE 6, the end head 112 of each unit is provided with an inlet coupling 116 which is in communication with a gas passage tube 118, the latter extending through an opening in the end head lid.

A balancing tube i2]! is in communication with the tube 118 in each of the sound-attenuating units to facilitate the balancing or neutralization of pressure impulses in the exhaust gas streams delivered into units res and 1.67. The inlet couplings 116 are connected respectively with the engine exhaust manifolds in the manner illustrated in FEGURE l. Partitions i122, i224 and 126 extend transversely within each sound-attenuating unit and with the end heads form gas passage and sound-attenuating chambers 128, 139;, 132 and 134.

The end head 112 is provided with an outlet coupling 1% in communication with a gas passage means or tube 138 which extends through the partitions and is surrounded by a tube 40. T he annular space between the tubes 133 and is subdivided into lengthwise arranged compartments by means of annular spacers providing high frequency sound-attenuating chambers or regions I244.

The tubes 1118, 133 and 149 have their well regions provided with a large number of comparatively small openings or orifices which facilities transverse flow of exhaust gases and eventual discharge through the outlet i 136 in each unit. The openings in the walls of the gas passage tubes and the tube form acoustic couplings with the adjacent chambers or compartments for attenuating sound Waves. The gas passage means opens into the resonator chamber 134 which serves to attenuate sound waves in the low frequency range.

In the arrangement shown in FIGURE 6, the inlet gas passage means in each of the units 135 and 167 are in alignment and communicate with each other through the medium of the connecting means or pressure balancing tube is t The pressure balancing tube ins iacilitates the equalization of unequal or irregular pressure impulses in the individual exhaust gas streams so as to improve the attenuation or damping of the sound waves established by pressure impulses and to facilitate smoothing out the irregular pressure impulses in the exhaust streams.

FIGURE 7 illustrates a modified form of dual unit system for attenuating sound waves and balancing neutralizing irregular pressure impulses in dual gas streams. In this form, the system includes substantially identical sound-attenuating units or mufiiers and 152, the double wall shell construction 154 of each unit being uostantially the same as that shown in FEGURE 3. Each of the units is provided with end heads or end closures 156 and 158, the outer end closures 156 being provided with openings accommodating an inlet coupling 7.6% and an outlet coupling 162, the heads being flanged and sealed to tl e peripheral end regions or the shell 154.

Partitions 16:; extend transversely Within the shell and form gas transfer and sound-attenuating compartments 166 and a low frequency resonator chamber 163, the end closure 155i forming a Wall of the resonator chamber. The inlet couplings 160 is in communication with an inlet gas passage means or tube 17%) and the outlet coupling 162 is in communication with a second gas passage tube or means 172.

The tube 172, is surrounded by a tube 174 of larger diameter, the annular regions surrounding the tube 172 between adjacent spacers 1'76 forming high frequency soundattenuating compartments 0r chambers. The Walls of the tubes 17%, 172. and 1.74 are provided With lar e number of comparatively small openings 18b to facilitate transverse llow of gases through the chambers 165 to the discharge tube 172 and discharge outlet 162. The openiugs provide acoustic coupling means for attenuating sound waves in the high frequency range.

The adjacent end heads or closures 153 are formed with openings to accommodate or receive a connecting tube which provides means for equalizing unequal pressures or pressure impulses in the attenuating units 1 3 and 1522 resulting from irregular pressure impulses in the exhaust gas streams. In this form, the pressure balancing tube E82 opens into the low frequency resonator chambers 3 .63 in each unit, and, as illustrated, the tube 182 is aligned With and spaced lengthwise from the gas passage tubes 172. The chambers 163 facilitate substantially unimpeded transfer of gases from the ends of the gas passage tubes 17%) to the balancing tube 132 to facilitate equalization of pressure impulses in the gas streams.

FIGURE 8 illustrates a modified form of gas pressure blending and sound-attenuating system of the invention. In this arrangement the system is inclusive of substantially identical sound-attenuating and gas blending units or muiilers 319i and 192, the shell construction 1% being preferably of the double wall arrangement of the character illustrated in the form of the invention shown in FIG- URE 3. Each of the sound-attenuating units is provided with an end head or end closures 3% and 1% which are secured to the muiller shell 1% in the same manner illustrated in FIGURE 3.

in the muffler arrangement shown in FlGURE 8, each muiiler unit 'ncludes transversely extending partitions 1% subdividing the interior into gas transfer compartments and resonator chambers and 202, the end closures and forming walls of resonator chambers.

113011 of the mufiler units includes an inlet coupling i which is in communication with a first gas passage means or tube 2% which extends through openings in the partitions 1% and opens into the resonator chamer 2%. Each unit includes a second gas passage tube 2&8 and a third gas passage tube 21%.

A tubular member surrounds the second gas passage tube .68 and the regions between the tube 238 and the tubular member 212 provide chambers for the attenuation of high frequency sound waves. The walls of all the gas passage tubes within each mutller and between the end partitions 193 are formed with a large number of comparatively small openings to facilitate transverse flow of gas through the compartments 2th). The openings in the Walls of the tubes form acoustic couplings with the adjacent regions in order to attenuate sound waves of the gas streams.

It should be noted that the regions or wall portions of the tubes 2M and 21d projecting respectively through the low frequency sound-attenuating chambers 261 and 2132 are unperforated, a factor which compels traverse of the gases through longer paths in the mufiier units. The end heads 196 of the muffler units of FIGURE 8 are connected by means of a balancing tube 216 for equalizing unequal pressure impulses in the exhaust gas streams.

In this form of the invention, a gas discharge outlet 21% is connected with the balancing tube 216 and through which the gases from both muffler units are discharged througuh a common outlet passage 218. The balancing tube 216 and the gas discharge tube or passage 218 should be of sufficient cross-sectional area to accommodate the volume of gases from both units 196 and 192 with a minimum of back pressure.

FIGURE 9 illustrates a pressure impulse balancing and sound-attenuating system for dual streams of exhaust gases from an internal combustion engine, each mufller of the unit embodying a combined gas inlet and outlet construction. The sound-attenuating units 230 and 232 include shell constructions 234, end heads 246 and 250 and interior components comprising transversely extending partitions 236, a first gas passage tube 238, a second gas passage tube 24% and a tubular member 242 surrounding the second passage tube.

These compcnents are of the same construction and arrangement as the corresponding components illustrated in the sound-attenuating units 15% and 152 of FIGURE 7. The adjacent end heads or closures 246 are provided with openings to accommodate a connecting or pressure balancing tube 243 which corresponds in function with the balancing tube 132; shown in FIGURE 7. Each of the outer end heads 25% of the sound-attenuating units is provided with an inlet opening 252 and an outlet opening 254.

A fitting 256 is fashioned of tubular components to provide a combined inlet and outlet construction or unit to accommodate delivery of the streams of exhaust gases into the units and 2.32 and accommodate the discharge of gases from both units. Each fitting 256 comprises a tubular portion 258 extending lengthwise of the vehicle and normal to the longitudinal axes of the soundattenuating units. Joined by Welding or other means to the tubular member 253 is a tubular gas inlet member 2619 and a tubular gas outlet member 262.

Disposed within the tubular member 258, intermediate the connections of tubular members 26% and 262 therewith, is an abutment or plug 264 which is sealed within the tubular member 258 and compels delivery of exhaust gases from an exhaust manifold through the inlet opening 252 into the sound-attenuating unit. The portion of the tubular member 253 rearward of the outlet passage 262 may be connected with an exhaust pipe for conveying the discharged exhaust gases rearwardly of the vehicle.

Thus the fittings 256, associated with each of the sound-attenuating units 238 and 232, provide a simple, yet effective, means for conveying the exhaust gases into and away from the attenuating units. It is to be understood htat the fitting arrangement 256 may be utilized with the forms of the invention illustrated in FIGURES 1 through 7.

The balancing tubes connecting the sound-attenuating units in all forms of the invention discolsed may be disposed amidship of the vehicle and adjacent the drive shaft construction 26 as shown in FIGURE 2 to obtain maximum clearance between the mufilers or sound-attenuators and the roadway. The balancing tubes may be bent downwardly at their central regions to obtain further additional clearance for the mufiier constructions. The primary function of the balancing tube in all forms of the invention is to further the equalization or balancing of gas pressures or pressure impulses in the soundattenuating units.

It is apparent that, Within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

1 claim:

1. An exhaust system for an internal combustion engine having dual exhaust manifolds including a pair of sound attenuating mufilers disposed in longitudinally aligned spaced relation, each of said mufflers being formed with gas inlet means and gas outlet means, pipes connecting the manifolds with the inlet means respectively, gas passage tubes in each of the mufiiers disposed in parallel transversely spaced relation, transversely a.- ranged walls in each of said mufilers forming compartments in the mufflers, the walls of the gas passage tubes being for-med with a plurality of comparatively small openings, said openings forming acoustic couplings with the compartments for attenuating sound waves and accommodating transverse flow of exhaust gases through the compartments, and a single duct of lesser cross sectional area than that of either mutfler connecting the spaced mufiiers providing pressure balancing means between the mufflers.

2. An exhaust system for an internal combusion engine having dual exhaust manifolds including a pair of elongated mufflers disposed in longitudinally aligned spaced relation, each of said mufilers being formed with gas inlet means and gas outlet means, pipes connecting the respective manifolds with the inlet means, gas passage means in the mufliers including a tube in each muifier in registration with the inlet means, a second gas passage tube in each of said mufliers in registration with the outlet means, transversely arranged baffle means disposed in each of said mufllers forming compartments in the muffiers, the walls of the gas passage tubes being formed with a plurality of comparatively small openings, said openings forming acoustic couplings with the compartments for attenuating sound waves and accommodating transverse flow of exhaust gases in the compartments, and a single duct of lesser cross section than that of either of the mufflers connecting the spaced muifiers providing pressure balancing means between the mufilers.

3. Apparatus for attenuating sound waves of gas streams including, in combination, a pair of sound wave attenuating units arranged in longitudinally spaced aligned relation, each of said units comprising an elongated hollow shell and closures secured to the ends of the shell, each of the outer end closures of the units being provided with a gas inlet and a gas outlet, a pair of tubular gas passage means in each shell, one of said tubular gas passage means being in registration with the gas inlet and the other in registration with the gas outlet, each of the adjacent end closures of the units having an opening formed therein, a single connecting tube extending through the openings in the adjacent end closures establishing gas passage means between the units, the walls of the tubular gas passage means in each of the units being formed with a plurality of comparatively small openings forming acoustic couplings and providing for transverse flow of gases within each unit from one tubular means to the other.

4. Apparatus for attenuating sound waves of gas streams including, in combination, a pair of sound Wave attenuating units arranged in spaced longitudinally aligned relation, each of said units comprising an elongated hollow shell and closures secured to the ends of the shell, each of the outer closures of the units being provided with a gas inlet and a gas outlet, gas passage tubes disposed in each shell, one of said gas passage tubes being in registration with the gas inlet and the other in registration with the gas outlet, the walls of the gas passage tubes having open areas formed therein, each of the inner end closures of the units having an opening formed therein, and a single connecting tube extending through the openings in the inner end closures establishing gas passage means between the units.

5. Sound attenuating apparatus for use with dual exhaust gas streams from an internal combustion engine of a vehicle including, in combination, a pair of sound attenuating units adapted to be disposed in aligned relation transversely of the vehicle, each of said units comprising an elongated hollow shell and closures at the ends of the shell, sound attenuating means contained within each of said units, the adjacent ends of the units being in spaced relation, openings formed in the adjacent end closures, a pressure equalizing tube registering with the openings establishing communication between the units, each of the opposite end closures of the units being provided with exhaust gas inlet and outlet openings, a tubular fitting disposed adjacent each of the opposite end closures including a tubular portion arranged normal to the axis of the adjacent unit, a pair of tubes joined with the tubular portion and extending in direction normal to the tubular portion and into the inlet and outlet openings in an end closure, and means in the tubular portion influencing the gases to flow into the adjacent unit through one of the tubes and away from the unit through the other of said tubes.

6. Sound attenuating apparatus for use with dual exhaust gas streams from an internal combustion engine of a vehicle including, in combination, a pair of sound attenuating units adapted to be disposed in aligned relation transversely of the vehicle, each of said units comprising an elongated hollow shell and closures at the ends of the shell, sound attenuating means contained Within each of said units, the adjacent ends of the units being in spaced relation, a pressure equalizing tube connecting adjacent ends of the units establishing communication between the units, the outermost end closures of the units being provided with exhaust gas inlet and outlet openings, a tubular fitting disposed adjacent each of the outermost end closures including a tubular portion arranged normal to the axis of the adjacent unit, each of said fittings having a pair of tubes joined with the tubular portion and extending in directions normal to the tubular portion and into the inlet and outlet openings in an outermost end closure, and a wall in said tubular portion disposed between the regions of connection of the tubes with the tubular portion.

Sheldrick Apr. 27, 1937 Muller Aug. 29, 1944 (Other references on following page) 11 UNITED STATES PATENTS Marx Oct. 30, 1951 187,171 Bryant Oct. 21, 1952 124,337 Trembley Nov. 10, 1953 506,100 Maxim Oct. 19, 1954 5 1,021,641 Powers June 27, 1961 1, 7

.14.. FOREIGN PATENTS Great Britain Oct. 19, 1922 Austria Sept. 10, 1931 Belgium Oct. 15, 1951 Germany Dec. 27, 1957 France Feb. 16, 1959 

